Optical aperture for data recording having transmission enhanced by waveguide mode resonance

ABSTRACT

Electromagnetic radiation from an optical source is directed onto an optical aperture in a metallic structure. The metallic structure in turn emits optical output from an emission region in the structure and onto a recording medium (e.g., a magnetic recording disk), thereby heating the medium. The optical output is enhanced when the electromagnetic radiation from the optical source includes a frequency that matches a waveguide mode resonance in the metallic structure. Features (such as ridges or trenches) in the metallic structure may be used to further increase the emitted optical output beyond what the emitted optical output would be in the absence of these features. The apparatus and associated method are useful for data recording, e.g., thermally assisted data recording.

RELATED APPLICATIONS

This application is a continuation-in-part of and claims priority toApplicant's copending application Ser. No. 10/026,029, filed Dec. 18,2001 and entitled “Optical aperture for data recording havingtransmission resonance enhanced by surface plasmon resonance”.

TECHNICAL FIELD

The invention relates to thermally-assisted data recording, in which aregion of a recording layer (e.g., a magnetic layer) is brought to anelevated temperature as part of the data recording process, and moreparticularly to near-field optical techniques for accomplishing thisheating.

BACKGROUND

Magnetic recording disk drives store digital information by using a thinfilm inductive write head. The write head is patterned on the trailingsurface of a slider that also has an air-bearing surface (ABS) to allowthe slider to ride on a thin film of air above the surface of therotating disk. The write head is an inductive head with a thin filmelectrical coil located between the poles of a magnetic yoke. When writecurrent is applied to the coil, the pole tips provide a localizedmagnetic field across a gap that magnetizes the recording layer on thedisk into one of two distinct magnetic states (binary data bits).

The magnetic material used as the recording layer on the disk is chosento have sufficient coercivity that the magnetized data bits are writtenprecisely and retain their magnetization state until written over by newdata bits. The data bits are written in a sequence of magnetizationstates to store binary information in the drive, and the recordedinformation is read back with a read head that senses stray magneticfields generated from the recorded data bits. Magnetoresistive (MR) readheads include those based on anisotropic magnetoresistance (AMR), giantmagnetoresistance (GMR), such as the spin-valve type of GMR head, andthe more recently described magnetic tunnel junction (MTJ) effect. Boththe write and read heads are kept in close proximity to the disk surfaceby the slider's ABS, which is designed so that the slider “flies” overthe disk surface as the disk rotates beneath the slider.

Disk drive areal data density (the number of bits that can be recordedon a unit surface area of the disk) is now approaching the point wherethe grains that define data bits are so small (about 8 nanometersacross) that they can be demagnetized simply from thermal agitationwithin the magnetized bit (the so-called “superparamagnetic” effect).The conventional approach to circumventing this problem is to increasethe magneto-crystalline anisotropy and coercivity of the magneticmaterial in the disk's recording layer to improve the thermal stability.This has required that the write head be made with materials havingincreasingly high saturation moments, thereby increasing the write fieldof the head so it can write on the high coercivity media. However, thesaturation moment is limited by the available materials. Sincecoercivity is temperature dependent, one proposed solution isthermally-assisted magnetic recording (TAMR), in which the magneticmaterial in the recording media is locally heated during the writingprocess so that the coercivity is reduced enough for writing to occur—atroom temperature the coercivity is high enough that the recorded bitsare thermally stable.

Several approaches to TAMR have been proposed, including the use of alaser beam to heat the magnetic recording layer, as described in “DataRecording at Ultra High Density”, IBM Technical Disclosure Bulletin,Vol. 39, No. 7, July 1996, p. 237; “Thermally-Assisted MagneticRecording”, IBM Technical Disclosure Bulletin, Vol. 40, No. 10, October1997, p. 65; and IBM's U.S. Pat. No. 5,583,727. A read/write head foruse in a TAMR system is described in U.S. Pat. No. 5,986,978, wherein aspecial optical channel is fabricated adjacent to the pole or within thegap of a write head for directing laser light (or heat) down thechannel. However, these technologies are generally limited to a heatedspot size in the recording medium on the order of a wavelength of thelight source.

Some recent scientific developments have underscored the dramaticoptical behavior of metallic structures when surface electromagneticresonances are excited. It had been thought that optical transmissionthrough sub-wavelength apertures was exceedingly small, varying as(d/λ)⁴ as first worked out theoretically by H. A. Bethe (“Theory ofDiffraction by Small Holes”, The Physical Review, vol. 66 (7-8), pp.163-182, October 1944). Ebbessen et al. have described the use ofsub-wavelength aperture arrays in a metal film to excite surfaceplasmons and enhance light transmission through the apertures. (See, forexample, European Patent Application EP 1 008 870 to Ebbesen et. al.,“Enhanced optical transmission apparatus utilizing metal films havingapertures and periodic surface topography”.) However, this work does notdisclose structures useful for data recording. Other investigators havedescribed the use of an aperture in a metal film on the face of a laserdiode for producing a near-field optical spot for optical datarecording. (See A. Partovi et al., “High-power laser light source fornear-field optics and its application to high-density optical datastorage”, Applied Physics Letters, vol. 75, pp. 1515-1517, 13 Sep.1999.) Although spot sizes of 250 nanometers were demonstrated, theabsence of resonant structures is expected to result in relatively lowtransmission for smaller spot sizes. Other researchers have investigatedtransmission resonances in waveguides and their relationship to periodicboundary conditions and film thickness (see J. A. Porto et al.,“Transmission resonances on metallic gratings with very narrow slits,”Physical Review Letters, vol. 83, no. 14, pp. 2845-2848, Oct. 4, 1999);still others have demonstrated that surface-enhanced transmission can beobtained from an individual aperture in a metal film in the presence ofbumps or divots (see D. E. Grupp et al., “Beyond the Bethe Limit:Tunable enhanced light transmission through a single sub-wavelengthaperture,” Adv. Mater., 1999, vol. 11, pp. 860-862). There is still aneed for a high intensity light (or heat) source that can be directed toa very small region of a data recording layer.

SUMMARY OF THE INVENTION

One embodiment of the invention is an apparatus for facilitating therecording of data. The apparatus includes an optical source and ametallic structure having an optical aperture therein. The aperture hasa first end and a second end, with the first end receiving opticalradiation from the source and the second end emitting optical output.The structure has a transmission resonance corresponding to a waveguidemode of the aperture, in which the transmission resonance is at afrequency that matches a frequency of the optical radiation, therebyenhancing the optical output from the second end beyond what the opticaloutput would be in the absence of the resonance. The emitted opticaloutput includes a near-field portion that extends from the structure outto a distance less than the average wavelength of the emitted opticaloutput. The apparatus also includes at least one element secured to themetallic structure, with said at least one element generating magneticfields whose strength is sufficient to write data in a data recordingmedium located within the near-field portion. The said at least oneelement advantageously includes at least one poling piece for applying amagnetic field in a portion of a storage medium as the emitted opticaloutput from the emission region heats the portion.

In a preferred embodiment, the optical aperture extends through thestructure; the optical aperture is preferably a slit filled withdielectric material. In a preferred embodiment, the dimensions of theaperture are selected to enhance the transmission of the opticalradiation at a predetermined frequency. The length of the aperture alongan optical axis thereof is preferably about ¼-½ that of the averagewavelength of the optical radiation from the source, and the aperturepreferably has a spatial dimension that is less than ½ that of theaverage wavelength of the optical radiation from the source. The opticalradiation from the source may advantageously have a fall width halfmaximum (FWHM) of less than about 0.1 times the average wavelength ofthe optical radiation.

In one preferred embodiment, there is provided a platform (e.g., aslider having an air-bearing surface) to which the structure and said atleast one element are secured, in which the platform is configured to bemoved relative to a data recording medium while the separation betweenthe structure and a surface of the data recording medium is kept to lessthan the average wavelength. This separation is advantageously nogreater than the near-field distance. The metallic structure preferablyincludes metal selected from the group consisting of Au, Ag, Cu, Al, andCr. In a preferred embodiment, the structure includes at least onefeature on each of opposite sides of the aperture, with the featuresenhancing the optical output from the structure. In one preferredembodiment, the features include variations in the thickness of thestructure.

In one aspect of the invention, there is provided a method of directingelectromagnetic radiation onto a data recording medium. The methodincludes providing a metallic structure having an optical aperturetherein, with one end of the aperture receiving optical radiation andanother end of the aperture emanating optical output away from thestructure, in which the structure has a transmission resonancecorresponding to a waveguide mode of the aperture. The method includesdirecting optical radiation into the aperture at a frequency thatmatches the transmission resonance to enhance the optical output, anddirecting the optical output onto a data recording medium to facilitatethe recording of data. The data is preferably readable by a processor.The method may further advantageously include applying a magnetic fieldto the recording medium to write data into the recording medium, and therecording medium may be heated with the optical output; the datarecording medium and the metallic structure are advantageouslypositioned to within a wavelength of each other. In a preferredimplementation of the invention, the recording medium is granular andhas a grain size on the order of between 10 and 250 cubic nanometers.The recording medium may include a medium selected from the groupconsisting of magneto-optic, phase-change, and chemical change media.

In another aspect of the invention, there is provided a method ofdirecting electromagnetic radiation onto a recording medium. The methodincludes providing a metallic structure having an optical aperturetherein, in which the structure has a transmission resonancecorresponding to a waveguide mode of the aperture. The method furtherincludes directing optical radiation into the aperture at a frequencythat matches the transmission resonance to enhance optical outputpropagating out of the aperture and away from the structure, directingthe optical output onto a recording medium to heat the recording medium(thereby facilitating the recording of data), and reading back the datawith a processor.

In one aspect of the invention, there is provided a method of directingoptical radiation onto a data recording medium. The method includesproviding a metallic structure having an optical aperture therein, withthe structure having dimensions selected to support optical radiationpropagating in a waveguide mode of the aperture. The method alsoincludes resonantly coupling optical radiation into the metallicstructure, in which the optical radiation includes a frequency thatmatches a transmission resonance of the waveguide mode, and furtherincludes directing optical output from the structure onto the datarecording medium.

Another embodiment of the invention is a laser that includes an opticalgain medium through which optical radiation is amplified, and a firstreflector and a second reflector disposed around the gain medium. One ofthe reflectors includes at least one emission region though whichoptical output is emitted (in which the emission region has a crosssection having at least one spatial dimension no greater than an averagewavelength of the optical output), as well as a metallic structurehaving an array of features that couple the radiation to at least onesurface plasmon mode of the structure to increase the emitted opticaloutput from the emission region beyond what the emitted optical outputfrom the emission region would be in the absence of the features. In apreferred embodiment, the laser is secured (directly or indirectly) to aplatform, in which the platform is configured to be moved relative to adata recording medium while the separation between the emission regionand a surface of the data recording medium is kept to less than theaverage wavelength. The platform may advantageously include anair-bearing surface. In another preferred embodiment, the spacingbetween the features in the array is chosen to enhance the opticaloutput from the emission region at at least one predetermined frequency.In one preferred embodiment, at least one element is secured (directlyor indirectly) to the laser, with said at least one element generatingmagnetic fields whose strength is sufficient to write data in a datarecording medium located within a near-field portion of the opticaloutput.

Yet another embodiment of the invention is a laser that includes anoptical gain medium through which optical radiation is amplified and afirst reflector and a second reflector disposed around the gain medium.One of the reflectors includes a metallic structure having an opticalaperture therein, in which the aperture has a first end and a secondend, with the first end receiving optical radiation from the medium andthe second end emitting optical output. The structure has a transmissionresonance corresponding to a waveguide mode of the aperture, in whichthe transmission resonance is at a frequency that matches a frequency ofthe optical radiation, thereby enhancing the optical output from thesecond end beyond what the optical output would be in the absence of theresonance. In a preferred embodiment, the laser is secured (directly orindirectly) to a platform, with the platform being configured to bemoved relative to a data recording medium while the separation betweenthe structure and a surface of the data recording medium is kept to lessthan an average wavelength of the optical output. This platform mayadvantageously include an air-bearing surface. At least one element maybe secured (directly or indirectly) to the laser, with this elementgenerating magnetic fields whose strength is sufficient to write data ina data recording medium located within a near-field portion of theoptical output.

Preferred embodiments and implementations of the invention may beapplied to a variety of technologies that record on a rigid surface(such as magnetic, phase-change, and chemical-change).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a planar view of an exemplary magnetic disk drive;

FIG. 2 is an end view of a slider with a magnetic head of the disk driveas seen in plane 2—2;

FIG. 3 is an elevation view of the magnetic disk drive wherein multipledisks and magnetic heads are employed;

FIG. 4 is an isometric illustration of an exemplary suspension systemfor supporting the slider and magnetic head;

FIG. 5 is an ABS view of the slider taken along in plane 5—5 of FIG. 2;

FIG. 6 is a partial view of the slider and magnetic head as seen inplane 6—6 of FIG. 2;

FIG. 6A is an expanded view of a portion of the device shown in FIG. 6;

FIG. 7 is a partial ABS view of the slider taken along plane 7—7 of FIG.6 to show the read and write elements of the magnetic head;

FIG. 8 is a view taken along plane 8—8 of FIG. 6 with all material abovethe write coil removed;

FIGS. 9A and 9B show a partial cross sectional end view and an ABS view(of the same orientation as FIG. 7), respectively, of an optical devicethat includes an optical resonance member having ridges in a metalliclayer and an aperture through which optical radiation is emitted;

FIG. 9C is an ABS view of an optical device that includes an opticalresonance ember whose elements are oriented at 90 degrees with respectthose of the embodiment of FIGS. 9A and 9B;

FIGS. 9D and 9E show an ABS and a partial cross sectional end view (ofthe same orientation of FIG. 6A), respectively, of an optical devicethat includes an optical resonance member having a step edge and anaperture through which optical radiation is emitted;

FIG. 9F shows one preferred embodiment that integrates an opticalresonance member with a write head;

FIG. 10 shows a partial cross sectional end view (of the sameorientation as FIG. 6A) of an optical device that includes an opticalresonance member having trenches in a metallic layer and an aperturethrough which optical radiation is emitted;

FIGS. 11A and 11B show a partial cross sectional end view and an ABSview (of the same orientation as FIG. 7), respectively, of an opticaldevice that includes an optical resonance member having ridges in ametallic layer and a protrusion member from which optical radiation isemitted;

FIGS. 12A and 12B show how electric charge densities in a metallic layer(having an aperture that supports a waveguide mode resonance), as wellas electric fields across the aperture, vary over time;

FIG. 13 is cross sectional view of an embodiment in which a light sourceis integrated with a slider;

FIGS. 14A and 14B are air bearing surface and partial cross sectionalviews, respectively, of the optical device of FIG. 13;

FIG. 15A is a scanning electron micrograph image of an array of holes ina silver film deposited on quartz;

FIG. 15B shows the transmission spectrum of diffracted light(zero-order) through a structure similar to the one shown in FIG. 15A;

FIG. 15C shows experimental and theoretical transmission (as a functionof hole diameter) for structures similar to the one shown in FIG. 15A;

FIG. 16A shows a scanning electron micrograph image of a grating made insilver (on quartz) in which the spacing between adjacent slits is equalto 450 nanometers;

FIGS. 16B, 16C, and 16D show transmission spectra through silvergratings similar to the one shown in FIG. 16A, in which the slit spacingis 225 nanometers, 330 nanometers, and 450 nanometers, respectively, andin which surface plasmon (SP) and waveguide (WG) mode resonances areindicated;

FIG. 17 shows additional transmission data through a silver (on quartz)grating (slit spacing of 450 nanometers) for film thicknesses of 225nanometers and 300 nanometers;

FIG. 17A shows additional transmission data through a silver (on quartz)grating (slit spacing of 450 nanometers) for a film thickness of 225nanometers, and for comparison, data through a tungsten (on quartz)grating (slit spacing of 450 nanometers) for a film thickness of 225nanometers.

FIG. 18A is a scanning electron micrograph image of a silver (on quartz)film structure having a single slit (of width 35 nanometers) between 120nanometer high ridges (in the metal film) separated by 450 nanometers.

FIG. 18B shows transmission spectra for structures consisting of asingle, isolated 35 nanometer wide slit in 225 nm thick silver andtungsten films (on quartz), respectively; and

FIG. 18C shows a transmission spectrum for the structure shown in FIG.18A.

DETAILED DESCRIPTION OF THE INVENTION Magnetic Disk Drive

Referring now to the drawings wherein like reference numerals designatelike or similar parts throughout the several views, FIGS. 1-3 illustratea magnetic disk drive 30. The drive 30 includes a spindle 32 thatsupports and rotates a magnetic disk 34. The spindle 32 is rotated by amotor 36 that is controlled by a motor controller 38. A combined readand write magnetic head 40 is mounted on a slider 42 that is supportedby a suspension 44 and actuator arm 46. A plurality of disks, slidersand suspensions may be employed in a large capacity direct accessstorage device (DASD) as shown in FIG. 3. The suspension 44 and actuatorarm 46 position the slider 42 so that the magnetic head 40 is in atransducing relationship with a surface of the magnetic disk 34. Whenthe disk 34 is rotated by the motor 36, the slider is supported on athin (typically in the range of 5-20 nanometers, e.g., 15 nanometers)cushion of air between the surface of the disk 34 and an air bearingsurface (ABS) 48 of the slider 42. The magnetic head 40 may then beemployed for writing information to multiple circular tracks on thesurface of the disk 34, as well as for reading information therefrom.Processing circuitry 50 exchanges signals, representing suchinformation, with the head 40, provides motor drive signals for rotatingthe magnetic disk 34, and provides control signals for moving the sliderto various tracks. The components described hereinabove may be mountedon a frame 54 of a housing 55, as shown in FIG. 3. In FIG. 4 the slider42 is shown mounted to the suspension 44.

FIG. 5 is an ABS view of the slider 42 and the magnetic head 40. (In theABS views herein, the trailing edge is taken to be at the top of thefigure.) The slider has a center rail 56 that supports the magnetic head40, and side rails 58 and 60. The rails 56, 58 and 60 extend from across rail 62. With respect to rotation of the magnetic disk 34, thecross rail 62 is at a leading edge 64 of the slider and the magnetichead 40 is at a trailing edge 66 of the slider.

FIG. 6 is a side cross-sectional elevation view of the merged MR head40, which includes a write head portion 70 and a read head portion 72,the read head portion employing a sensor 74. FIG. 7 is an ABS view ofFIG. 6. The sensor 74 is sandwiched between first and second gap layers76 and 78, and the gap layers are sandwiched between first and secondshield layers 80 and 82. In response to external magnetic fields, theresistance of the sensor 74 changes. A sense current Is conductedthrough the sensor causes these resistance changes to be manifested aspotential changes. These potential changes are then processed asreadback signals by the processing circuitry 50 shown in FIG. 3.

As shown in FIG. 6, the write head portion of the merged MR headincludes a coil layer 84 sandwiched between first and second insulationlayers 86 and 88. A third insulation layer 90 may be employed forplanarizing the head to eliminate ripples in the second insulation layercaused by the coil layer 84. The first, second and third insulationlayers are referred to in the art as an “insulation stack”. The coillayer 84 and the first, second and third insulation layers 86, 88 and 90are sandwiched between first and second pole piece layers 92 and 94. Thefirst and second pole piece layers 92 and 94 are magnetically coupled ata back gap 96 and have first and second pole tips 98 and 100 which areseparated by a near-field resonance element 102 at the ABS 48. Theresonance element 102 (described in greater detail below) directselectromagnetic radiation onto the magnetic disk 34. The read/write head40 may be advantageously covered with an protective overcoat layer 103such as aluminum oxide.

As suggested by FIGS. 2 and 4, first and second solder connections 104and 106 connect leads (not shown) from the spin valve sensor 74 to leads112 and 114 on the suspension 44, and third and fourth solderconnections 116 and 118 connect leads 120 and 122 from the coil 84 (seeFIG. 8) to leads 124 and 126 on the suspension.

Preferred Embodiments Related to Waveguide Mode Resonance EnhancedOptical Transmission

In FIG. 6, an optical source such as a laser diode 200 is shown securedto the slider 42. Optical output from the diode 200 is directed througha waveguide 203 surrounded by a cladding 204. The waveguide 203 and thecladding 204 (not shown in FIGS. 2 and 4 for clarity) pass through theread/write magnetic head 40 such that the optical output is directedonto the resonance element 102. FIGS. 2 and 4 show the laser diode 200connected to leads 201, which in turn are connected to a power supply(not shown). The waveguide 203 and its cladding 204 are advantageouslysupported on the slider 42 and surrounded by protective material (notshown) such as alumina. Also, output from the laser diode 200 may becoupled into the waveguide 203 through a tapered optical element (notshown), such as those known to one skilled in the art.

An expanded view of the resonance element 102 and the components thatsurround it is shown in FIG. 6A. FIG. 9A is a partial cross sectionalend view of a preferred resonance element 102 showing the resonanceelement 102 adjoining the waveguide 203 and the cladding 204 surroundingthe waveguide. The resonance element 102 shown here includes dielectricmaterial 205 that joins the waveguide 203/cladding 204 to a metalliclayer 206. The metallic layer 206 may optionally include a single ridge207 (or alternatively, a periodic array of ridges) on both sides of anaperture 208, with the ridges protruding into the dielectric material205. (Alternatively, the ridges can be built into the waveguide 203without using the dielectric material 205.) The aperture 208 receivesoptical radiation from the waveguide 203 which is then directed onto themagnetic disk 34. The dimensions of the aperture 208 are advantageouslyselected so that it supports an electromagnetic waveguide mode having atransmission resonance at a desired frequency (which corresponds to acertain wavelength in air). By selecting input optical radiation at thissame frequency, the optical output emitted at the ABS end of theaperture 208 is advantageously resonantly increased. As discussed ingreater detail below, this waveguide mode resonance effect is differentfrom the surface plasmon effect discussed in Applicant's copendingapplication Ser. No. 10/026029 entitled “Optical aperture for datarecording having transmission resonance enhanced by surface plasmonresonance” filed Dec. 18, 2001, which is hereby incorporated byreference.

Using the preferred embodiments herein, track widths of 10-200nanometers, and more preferably 20-100 nanometers (which may correspondto aperture width ranges of about 5-100 nanometers and about 10-50nanometers, respectively, when the long axis of the aperture is parallelto the tracks), may be realized by appropriately choosing the dimensionsof the aperture 208. Preferred materials for the metallic layers in theoptical resonance elements described herein include Au, Ag, Cu, Al, andCr. With respect to the apertures herein, they may be optionallyprotected by filling them with dielectric material. In this sense theaperture 208 (as well as other apertures in the preferred embodimentsdescribed herein) may be more generally viewed as an “optical aperture”that is not necessarily an evacuated space, but that neverthelesssupports a waveguide mode having a corresponding resonance.

The metallic layers in the optical resonance elements herein mayadvantageously have a thickness in the range of 0.25 to 0.5 that of thewavelength (in vacuum or air) of the light source, e.g., a light sourcewhose optical emission has a wavelength in air of 650 nm could beadvantageously used with a metallic layer whose thickness is in therange of 325 to 163 nm. By way of example, these metallic layers mayadvantageously have a thickness between 100 and 1000 nm. The optionalfeatures disclosed herein (e.g., trenches and ridges, such as ridges207) enhance the emitted optical output from the aperture (beyond theoptical output obtained due the waveguide mode resonance effect in theabsence of such features) and may advantageously have lengths of100-1000 nanometers or greater, widths (if trenches or ridges are used)of 10-150 nanometers (more preferably 20-50 nanometers, e.g., about 35nanometers), and depths or heights of 20-300 nanometers (morepreferably, 40-200 nanometers, e.g., 120 nanometers); in addition, thespacing between the aperture and its adjacent features is preferablyless than 125-800 nanometers (or 150-300 nanometers, e.g., 225nanometers). The apertures herein may advantageously have widths (attheir narrowest point) in the range of 10-100 nanometers (morepreferably 10-50 nanometers) and lengths (measured along the aperture'soptical axis) that are long enough to prevent cutoff of the lowest ordermode of the aperture, e.g., on the order of approximately 0.5 times to0.25 times (depending on the shape of the aperture, e.g., whether theaperture has a notch) the average wavelength (in air) of the lightsource (e.g., 200-1000 nanometers, or 390-2000 nanometers). Thedielectric layers herein may advantageously have a thickness chosen tooptimize optical transmission. As used herein, the terms “light” and“optical” are intended to include visible, as well as invisible (e.g.,ultraviolet and infrared) electromagnetic radiation.

FIG. 9B shows the corresponding ABS view of the resonance element 102.The aperture 208 in the metallic layer 206 may optionally includenotches 220, as shown in FIG. 9B. A notch on one or both sides of theaperture 208 serves to further narrow the track width and increase theintensity of the light due to an antenna (geometrical) effect. Since thewaveguide 203, the cladding 204, and the ridges 207 are not visible whenviewed from the disk 34, the ridges 207 and the waveguide/claddinginterface 222 are shown here using dashed lines.

With respect to the device shown in FIGS. 6 and 6A, the various layersmay be deposited using additive and subtractive lithographic techniquesknown to those skilled in the art. With respect to FIGS. 9A and 9B, theresonance element 102 may be advantageously constructed subsequent tothe rest of the device by depositing layers onto the face of the devicethat becomes the air bearing surface.

FIG. 9C is an ABS view of an alternative embodiment that includes ametallic layer 206′ having a single ridge 207′ therein on each side ofan optical aperture 208′ (that passes through the metallic layer andincludes notches 220′), as well as dielectric material separating themetallic layer from a waveguide/cladding (with the boundary between thewaveguide and cladding indicated by the numeral 222′). In short, allthese elements have been rotated 90 degrees with respect to theircounterparts in FIG. 9B, so that they have the same orientation as therest of the read/write structure in FIG. 6 (e.g., the first and secondpole piece layers 92 and 94). In this case, the entire fabricationprocess may be carried out at the wafer level.

Instead of having a ridge or a trench on each side of an emissionregion, a step edge (i.e., a step transition in the thickness of themetallic layer) may be used. This is illustrated in FIGS. 9D and 9E,which show ABS and partial cross sectional end views of a step-edge typeembodiment. A step edge 223 forms part of the contour separating ametallic layer 206 b from a waveguide 203 b that is surrounded bycladding 204 b. (The interface between the cladding and the waveguide isdenoted by the numeral 222 b.) Also shown is an optical aperture 208 b(illustrated here as having dielectric material therein) that has a pairof notches 220 b.

FIG. 9F shows a preferred way of integrating an optical resonanceelement with a write head. A waveguide 203 c, surrounded by cladding 204c, acts as a conduit for light that is directed onto a metallic layer206 c that has an optical aperture 208 c therein (with the aperture 208c shown here as having dielectric material therein). Pole pieces P1 andP2 (made of NiFeCo, for example) provide the requisite magnetic fieldsfor writing data into the data recording medium (not shown in FIG. 9F),a process that is thermally assisted by the optical radiation emanatingfrom the aperture 208 c and onto the data recording medium. (Aprotective overcoat layer 234 may also be used.) The embodiment of FIG.9F can be more generally viewed as a combination of an opaque member (inthis case, a metal) having an optical emission region therein (e.g., aslit or optical aperture), with the opaque member being located betweentwo pole pieces.

The waveguide 203 in the various embodiments herein couples light (asused herein, this term includes electromagnetic radiation outside thevisible portion of the spectrum) to the optical resonance element 102.As discussed above, the light that is input into the apertureadvantageously includes a significant spectral component at a frequencythat matches a waveguide mode resonance supported by the aperture.(Alternatively, the frequency of the light may be tuned to match thefrequency of the waveguide mode resonance, which is determined by theaperture's dimensions and the material in which it is constructed.) Theeffect is a frequency specific resonant enhancement of the light emittedfrom the distal end of the aperture (the end nearest the air bearingsurface), which is then directed onto a data recording medium, with thedata recording medium advantageously being positioned within thenear-field of the emitted optical output. As discussed in more detail inthe experimental section below, the intensity of the electromagneticradiation directed onto the data recording medium may be still furtherenhanced by including features (such as ridges or trenches) about theaperture. The polarization of the light incident on the aperture isadvantageously perpendicular to the orientation of the ridges 207 andthe axis along the longer dimension of the aperture. It is believed thatthe presence of the features leads to an increase in the surface chargemotion around the optical aperture, thereby increasing the re-radiationof light on the opposing surface and a very large transmission factor.The effect is largest when metals with low optical absorption are used,such as gold, silver, copper, chromium, and aluminum. Thus, the aperture208 acts as an emission region; during writing, its distance over thedisk 34 is preferably kept within a wavelength of light (more preferablyto within 50 nanometers), so that an intense near-field optical field isdirected onto the recording medium. As discussed in more detail below,the near-field light intensity emanating from the aperture 208 isconsiderably enhanced over the transmission intensity one would expectin the absence of the waveguide mode resonance. Also, the presence ofthe notches 220 in the aperture 208 advantageously acts to furtherincrease the intensity of the light emanating from the aperture.

The features used herein to enhance transmission do not necessarily needto be on a particular side of the optical resonance element, and may besurrounded by one or more non-conducting materials. The individualfeatures themselves may have any one of a number of shapes (e.g.,circular, square, rectangular, elliptical, or linear), and if a latticeof features is used, the lattice may have any one of a number possiblepatterns (e.g., square, triangular, linear array of lines). Such alattice may be formed by any one of a number of nanolithographytechniques, including e-beam, focused ion-beam, interferometriclithography, EUV lithography, stamping, and self assembly processes.

The apertures herein (aperture 208 in FIG. 9B, for example) aresubstantially longer than they are wide. This geometry results in anenhancement of the optical intensity greater than that from an aperturethat is, for example, square-shaped or circular (as discussed in moredetail below). Additionally, the geometry of the aperture 208 is wellsuited for the application of magnetic recording, since the width of anaperture effectively defines the tracks in the magnetic disk 34. (Notethat in the embodiment of FIG. 9C, the notches 220′ help to confine theemitted optical radiation to a track that is narrower than would beobtained in the absence of notches.) The near-field radiation emanatingfrom the aperture 208 is used to heat a track within the disk 34,followed by the writing of bits into that track. In the context of waveguide-enhanced transmission, an aperture having a shape other than aslit may be used as an emission region, e.g., the shape of the aperturemay be chosen to create a desired near-field optical pattern or size,provided that the aperture can be constructed in such a way as tosupport a waveguide mode. Further, the size and depth of the aperturemay be selected to support a particular resonance. As discussed below,the emission region itself is not necessarily limited to an aperture. Aprotrusion such as a sharp comer or tip on a resonant structure may formpart of the emission region; the shape of the protrusion may be square,rectangular, conical, or the protrusion may include an edge designed toproduce the desired shape for the optical region. Also, such aprotrusion member may be offset relative to the aperture or a featureabout the aperture, thereby controlling the phase of the surfaceresonance at the emission region.

In general, if the emission region is a slit, it may be either parallelor perpendicular to the data track direction. One advantage of aparallel orientation is very narrow track width (suitable for recordingat areal densities of 1 Th/i² and higher), while a perpendicularorientation may result in less curvature to the bit shape and be easierto manufacture. In either case, the optical output emanating from theemission region is used to heat up a portion of the recording media,which when used in combination with a magnetic field orients themagnetic bit.

The in-track bit density may be determined, in part, by the fieldgradient produced by the magnetic pole pieces. In thermally-assistedmagnetic recording, it is not necessary in general to have a large fieldgradient, since a large thermal gradient exists at the trailing edge ofthe heated area. This thermal gradient is equivalent to a large fieldgradient since a magnetic recording medium has a temperature dependentcoercivity. Thus, it is sufficient that the pole pieces just provide alarge field that can be switched at high frequency for field-modulatedwriting of bits at the heated region's trailing edge. Field modulatedwriting allows the heated region to be elongated along the trackdirection (from an elongated aperture or slit) and still have a high bitdensity along the track. Because a large field gradient is not needed,the pole pieces may be larger and may be located further away from theheated region, while still providing a sufficiently large fieldamplitude.

FIG. 10 shows an alternative optical resonance element 102 a thatincludes dielectric material 205 a and a metallic layer 206 a. Themetallic layer 206 a includes trenches 224 (as opposed to the ridges 207of FIGS. 9A and 9B), but this embodiment is otherwise designed like andfunctions similarly to its counterpart of FIGS. 9A and 9B.(Alternatively, trenches could be built into the waveguide 203, withoutusing the dielectric material 205 a.) Optical radiation incident on theresonance element 102 a is directed through the aperture 208 and ontothe disk 34.

FIGS. 11A and 11B show yet another optical resonance element 102 b thatis similar to the resonance element 102 of FIGS. 9A and 9B, except forthe presence of a metallic protrusion member 230. The embodiment ofFIGS. 11A and 11B, as well as other embodiments herein, may include aprotective overcoat layer 234 (e.g., carbon, carbon nitride, siliconnitride, or dielectric material). In addition, dielectric material 205 bnow occupies the space that previously defined the slit 208. In thisembodiment, optical output emanates away from the distal end of thedielectric material 205 b (near the protrusion member) with theprotrusion member 230 itself acting as an optical emission member thatradiates and helps direct electromagnetic radiation onto the disk 34.

FIGS. 12A and 12B illustrate schematically how current densities are setup around an aperture. Electromagnetic radiation having a polarizationindicated by the arrow 253 is incident on an aperture 255 (that may beoptionally filled with dielectric material) within a metallic layer 257having (optional) ridges 259 therein. Electric fields (as indicated bythe arrows 261) are set up across the aperture 255, in accordance withthe induced charge that accompanies the current flowing within themetallic layer 257 on either side of the aperture. As shown in FIG. 12B,the electric fields are reversed at some later time, as the spatialrelationship between the electromagnetic plane wave and the metalliclayer changes, thereby reversing the sign of the induced charge. Awaveguide mode resonance occurs when the charge motion at one end of theaperture 255 has a phase opposite that of the charge motion at the otherend of the aperture. The spectral position of the waveguide moderesonance depends on the thickness of the metallic layer 257 (as well asthe aperture width, type of metal, and the spectral position of thesurface plasmon mode when side features such as ridges or trenches areused), and the wavelength of the peak transmission (in air) isapproximately 2-4 times the thickness of the metallic layer. Thus, themetallic layer 257 preferably has a thickness between c/2ν and c/4ν, andmay vary from 130 to 650 nm, for example. (Here v is the frequency ofthe plane wave, and c/ν=λ when the index of refraction is equal to 1.)If ridges 259 (or trenches) are used, they may be advantageouslypositioned a distance from the center of the aperture 255 less than thedistance used with a surface plasmon resonance embodiment (less thanabout c/1.5ν when quartz and silver are used). Additional detailsregarding the physics of waveguide mode resonances are discussed in J.A. Porto et al., “Transmission resonances on metallic gratings with verynarrow slits,” Physical Review Letters, vol. 83, no. 14, pp. 2845-2848,Oct. 4, 1999.

FIG. 13 shows a schematic cross section of an alternative embodiment, inwhich a light source such as a laser diode 302 is integrated with aslider 310 having an air bearing surface 312, with the laser diode 302being near a trailing edge 316 of the device. The laser diode 302 islocated near or adjacent to both a first pole piece 326 and aninsulating member 334 that surrounds coils 340 for generating a magneticfield. The laser diode 302 includes a first reflector, such as a facet350, and a second reflector 360 at the output side of the laser diode;it further preferably includes an n-type layer 364, an active layer 366(from which photons are emitted), and a p-type layer 368. In addition,the laser diode 302 may be advantageously secured to a substrate 374 forease of handling. (Alternatively, the laser diode 302 may be fabricatedon the same wafer as the read/write head.) Current is supplied to thelaser diode 302 with electrical leads (not shown) connected to then-type and p-type layers 364 and 368, respectively. The laser diode 302and the mounting element 374 are preferably covered with an overcoatlayer 376 made of carbon, for example. A second pole piece (not shown)may be included to enhance or tailor the write field.

FIGS. 14A and 14B are more detailed views of the laser diode 302 of FIG.13, with FIG. 14A showing an ABS view of the laser diode 302. FIG. 14Ashows (in dashed lines) an interface 380 between the n-type layer 364and the active layer 366, as well as an interface 382 between the p-typelayer 368 and the active layer 366. The second, or output, reflector 360here includes dielectric material 386 and a metallic layer 390 thatincludes ridges 392 therein. An optical aperture 396 (that mayadvantageously include notches 398 therein, and may be advantageouslyfilled with dielectric material) in the output reflector emits opticalradiation from laser diode 302 onto the magnetic disk 34. Thus, thesecond reflector 360 functions like the waveguide optical resonanceelements described herein. (Alternatively, the second reflector 360 maybe designed like the resonance elements described in Applicant'scopending application Ser. No. 10/026029, in which surface plasmons inthe metallic layer 390 act to enhance the transmission of opticalradiation through the aperture 396 beyond that which would pass throughthe aperture in the absence of the features in the metallic layer suchas the ridges 392.) The features in the second reflector 360 may includefeatures other than the ridges 392, e.g., trenches may be used. As inother embodiments disclosed herein, during the writing process theemission region (aperture) 396 is preferably kept to within a wavelengthof light of the magnetic disk 34, more preferably to within 75nanometers, and still more preferably to within 50 nanometers, so thatan intense near-field optical field is directed onto the recordingmedium 34.

One advantage of integrating the laser diode 302 and the slider 42 inthis fashion is that optical radiation that is not directed onto thedata recording medium may remain in the cavity of the diode laser 302,thereby increasing the efficiency of the laser diode. Another advantageis that the wavefront of the optical radiation within an edge-emittinglaser diode has a stable polarization to excite surface plasmons andcouple to an aperture.

The device of FIGS. 13 and 14A, B may be assembled by constructing theslider 310/pole piece 326/insulating member 334/coils 340 portion of thedevice in one set of steps, and separately constructing the laser diode302/mounting element 374 portion of the device in another set of steps.These portions of the device may then be integrated along their commoninterface 410 by placing them both on an optical flat and bonding themtogether with conductive epoxy or conductive solder; using a conductivebonding element permits electrical connections to be made at the sametime. At this point, gentle lapping of the assembled device may benecessary so that the substrate 374, laser 302, first pole piece 326,and slider 310 form a smooth, continuous surface. Before depositing theovercoat layer 376, the aperture 396 may be formed in the secondreflector 360 through the use of a focused ion beam or e-beamlithography. Techniques for assembling such components are discussed inU.S. Pat. No. 5,625,617 to Hopkins et al., which is hereby incorporatedby reference.

Experimental

In the experimental results that follow, the transmission of opticalradiation through metallic films on quartz substrates is explored.Metallic films are discussed that function like the metallic layers inthe optical resonance elements described herein, displaying transmissionresonances related to a waveguide mode. In addition, resonances relatedto surface plasmon behavior are also observed. Which of these effectsdominates at any frequency of interest depends on how the opticalresonance element is constructed; an optical resonance element may betailored for a waveguide mode or a surface plasmon resonance at a givenfrequency of interest.

FIGS. 15A and 15B illustrate surface plasmon enhanced transmissionthrough a square array of holes. FIG. 15A shows a scanning electronmicrograph image of an array of holes in a 150 nanometer thick silverfilm deposited on quartz (a quartz substrate was used for all thestructures in FIGS. 15-18). The diameter of the holes is 155 nanometers,and the distance between the holes is 450 nanometers. These holes wereformed by focused ion beam milling. FIG. 15B shows a transmissionspectrum of the diffracted light (zero-order) for an array like the oneshown in FIG. 15A, except that the holes have a diameter of 110nanometers. For the data of FIG. 15B (as well as for the othertransmission spectra herein), a collimated white light source was usedfor illumination at normal incidence while transmitted light wascollected with a microscope objective, a spectrophotometer, and a liquidnitrogen cooled CCD array. In FIG. 15B, transmission is normalized tothe fraction of the total area occupied by the holes. For a square arrayof holes, surface plasmon resonances occur at wavelengths given bya₀(i²+j²)^(−1/2)(e₁e₂/e₁+e₂)^(1/2), in which a₀ is the distance betweenholes, i and j are integers, and e₁ and e₂ are the real components ofthe dielectric function of the two materials at the interface. Surfaceplasmon resonances occur at the air-metal, A(i,j), and quartz-metal,Q(i,j), interfaces. The three lowest frequency modes, designated A(1,0),Q(1,1), and Q(1,0), are indicated. FIG. 15C shows transmission data(normalized to the fraction of the total area occupied by the holes) asa function of hole diameter for the Q(1,1) mode. Transmission above oneindicates that more light was transmitted though the holes than wasincident directly on the area occupied by the holes. Also shown is thetheoretical maximum Bethe transmission for an infinitely thin, perfectlyconducting metal screen with a single hole (see Durig et. al., J. Appl.Phys. 59, 3318, 1986). The relatively small transmission for such smallholes relative to holes larger than 150 nanometers (see Ebbesen et. al.,Nature 391, 667, 1998), suggests that a 2-dimensional array of holes maynot be optimum for generating intense near-field radiation for ultrahighdensity data recording purposes, particularly for hole sizes below about150 nanometers (even though the transmission is about 10 times largerthan the maximum predicted by theory in the case of no surface plasmonenhanced transmission).

Transmission can be increased substantially using geometries other thanan array of holes. FIG. 16A shows a scanning electron micrograph imageof a metallic grating (225 thick silver on quartz) having a slit widthof 50 nanometers and a slit spacing equal to 450 nanometers. FIGS. 16B,16C, and 16D show zero-order transmission spectra for slit spacings of225 nanometers, 330 nanometers, and 450 nanometers, respectively. ForFIGS. 16B, 16C, and 16D, transmission is normalized to the fraction ofthe total area occupied by the slits. Transmission above one indicatesthat more light was transmitted though the slits than was incidentdirectly on the area occupied by the slits. For these data (as well asthose of FIGS. 17 and 18), the incident collimated white light used todetermine transmission was polarized perpendicular to the slits withnormal incidence. FIG. 16B shows experimental data for a waveguide modetransmission resonance (labeled WG in the Figures). The surface plasmon(SP) mode peak position as a function of wavelength depends linearly onthe spacing between the slits according to λ=a₀[ε₁ε₂/(ε₁+ε₂)]^(1/2), inwhich a₀ is the distance between slits. The SP mode at the air interface(SP-A) is weak relative to the SP mode at the quartz interface (SP-Q).

FIG. 17 shows transmission resonance data through metallic gratings(laid out like the grating shown in FIG. 16A), having a slit width of 50nanometers, a slit spacing of 450 nanometers, and film thicknesses of225 and 300 nanometers. As suggested by FIG. 17, the spectral positionof the waveguide mode resonance is sensitive to the film thickness, butthe spectral location is relatively insensitive to film thickness in thecase of surface plasmon excitation. These data suggest that when using adiode laser emitting at 780 nanometers as the optical source forthermally assisted recording, a metallic layer having 50 nm wide slitsseparated by about 450 nanometers would be suitable for a waveguide moderesonance. On the other hand, a surface plasmon mode would be excited atan optical frequency corresponding to 630 nm. The data of FIG. 17A showthat both surface plasmon enhanced transmission and waveguide moderesonance transmission are substantially increased when using a highconductivity metal (such as Au, Ag, Al, Cr, and Cu) as opposed to a lowconductivity metal (such as tungsten).

As suggested by the data above, a waveguide mode resonance (or a surfaceplasmon resonance) may be generated not just with a regular array ofholes or slits, but also with an array in which all but one (or more) ofthe holes or slits in such a regular array is replaced with raised orlowered regions in the surface of the metal film, so that the metal filmincludes ridges or trenches (such as in the embodiments discussedherein). FIG. 18A shows a scanning electron micrograph image of ametallic (silver) film on quartz, in which the metallic film has asingle 35 nanometer wide slit or aperture (in the center of FIG. 18A)surrounded by an array of ridges. The array of ridges was formed bypatterning 120 nanometer deep trenches in the quartz substrate beforesilver was evaporated onto it. This kind of structure has substantiallygreater transmission than one having a single slit without anysurrounding ridges. FIG. 18B shows normalized transmission spectra forisolated single slits in 225 nanometer thick silver film and tungstenfilm, showing that the normalized transmission is much higher withsilver than with tungsten. FIG. 18C presents the normalized transmissionspectrum for the silver film of FIG. 18A, showing the waveguide (WG)mode resonance and surface plasmon (SP) resonance at the quartzinterface. The transmission of an isolated slit in a film of tungsten isshown for comparison (dotted line). The data of FIGS. 18B and 18C werecollected from a single slit, and accordingly, the numerical aperture ofthe collection optics has been taken into account when calculating thenormalized transmission. Other experimental results suggest that for thewaveguide mode resonance phenomena described herein, placing a singlefeature (e.g., ridge or trench) on each side of the aperture is just aseffective in enhancing the effective transmission as using multiplefeatures, i.e., the effective transmission through an aperturesupporting a waveguide mode can be increased at the waveguide moderesonance frequency by positioning a single feature (e.g., a trench orridge) on each side of the aperture, but employing additional featuresbeyond this does not seem to enhance the effective transmission.

As suggested by FIG. 18C, the silver film of FIG. 18A is tailored fortransmission at 650 nanometers when used in a surface plasmon mode andabout 715 nm when used at a waveguide mode resonance. Thus, a laserdiode at 650 or 715 nm and a silver film having a lattice constant ofabout 450 nanometers effectively transmit optical radiation at thesewavelengths. The transmission of this device is about 60 times larger at650 nanometers (plasmon mode) than for the isolated slit in the film oftungsten at the same wavelength, and 15 times larger at 715 nanometers(at the waveguide mode resonance) than for the isolated slit in the filmof tungsten. As suggested by the fact that the normalized transmissionis above one, this silver film device collects optical power over aregion much larger than the slit itself and transmits the powereffectively through a sub-wavelength opening. Note that the maximumtransmission for this 35 nanometer slit structure (in which thetransmission is approximately 10, see FIG. 18C) is approximately 1000times larger than for the 2-dimensional array of 40 nanometer diameterholes (for which the transmission is approximately 0.01, see FIG. 15C),indicating that an emission region in the form of a slit may beadvantageously used for ultrahigh density data recording.

Although the embodiments herein have been described principally withrespect to waveguide mode phenomena, analogous embodiments involvingsurface plasmon effects can be constructed by appropriately tailoring,for example, the input optical frequency and the distance between thefeatures around the aperture. In addition, although the recording ofinformation has been described herein principally with respect tomagnetic recording on a magnetic disk, embodiments of the invention maybe used in conjunction with other kinds of recording media, such asmagneto-optic, phase-change, or chemical-change, and may be caused orassisted by heating or photo-chemistry. The invention may be embodied inother specific forms without departing from its spirit or essentialcharacteristics. The described embodiments are to be considered in allrespects only as illustrative and not restrictive. The scope of theinvention is therefore indicated by the appended claims rather than theforegoing description. All changes within the meaning and range ofequivalency of the claims are to be embraced within that scope.

1. An apparatus for facilitating the recording of data, comprising: anoptical source; a metallic structure having an optical aperture therein,said aperture having a first end and a second end, said first endreceiving optical radiation from said source and said second endemitting optical output, said structure having a transmission resonancecorresponding to a waveguide mode of said aperture, wherein saidtransmission resonance is at a frequency that matches a frequency of theoptical radiation, thereby enhancing the optical output from said secondend beyond what the optical output would be in the absence of saidresonance, wherein the emitted optical output includes a near-fieldportion that extends from said structure out to a distance less than theaverage wavelength of the emitted optical output; and at least oneelement secured to said metallic structure, said at least one elementgenerating magnetic fields whose strength is sufficient to write data ina data recording medium located within the near-field portion.
 2. Theapparatus of claim 1, wherein said aperture extends through saidstructure.
 3. The apparatus of claim 1, wherein said structure includesa protrusion member that directs the optical output onto the recordingmedium.
 4. The apparatus of claim 1, further comprising a platform towhich said structure and said at least one element are secured, whereinsaid platform is configured to be moved relative to a data recordingmedium while the separation between said structure and a surface of thedata recording medium is kept to less than said average wavelength. 5.The apparatus of claim 4, wherein said separation is no greater thansaid near-field distance.
 6. The apparatus of claim 4, wherein saidplatform is a slider having an air-bearing surface.
 7. The apparatus ofclaim 1, wherein said optical source comprises a laser and said emissionregion is located at an output face of said laser.
 8. The apparatus ofclaim 1, wherein said optical aperture is filled with dielectricmaterial.
 9. The apparatus of claim 1, said optical source comprising anoptical waveguide coupled to a source of optical radiation.
 10. Theapparatus of claim 1, wherein said metallic structure includes metalselected from the group consisting of Au, Ag, Cu, Al, and Cr.
 11. Theapparatus of claim 1, further comprising a protective coating thatadjoins said metallic structure.
 12. The apparatus of claim 1, saidstructure comprising at least one feature on each of opposite sides ofsaid aperture, said features enhancing the optical output from saidstructure.
 13. The apparatus of claim 12, comprising two of saidfeatures.
 14. The apparatus of claim 12, said features includingvariations in the thickness of said structure.
 15. The apparatus ofclaim 12, said features including a material other than a materialmaking up the rest of said metallic structure.
 16. The apparatus ofclaim 1, further comprising one or more dielectric coatings that adjoinsaid metallic structure, said one or more coatings having thicknessesselected to enhance the transmission of the optical radiation throughsaid apparatus.
 17. The apparatus of claim 1, wherein said aperture is aslit.
 18. The apparatus of claim 1, wherein said aperture has a width atits narrowest point of about 10-100 nanometers.
 19. The apparatus ofclaim 1, further comprising a protrusion member near said second end.20. The apparatus of claim 1, said at least one element comprising atleast one poling piece for applying a magnetic field in a portion of astorage medium as the emitted optical output from said emission regionheats the portion.
 21. The apparatus of claim 1, wherein the thicknessof said metallic structure is between 100 and 1000 nanometers.
 22. Theapparatus of claim 1, wherein the dimensions of said aperture areselected to resonantly enhance the transmission of the optical radiationat a predetermined frequency, and wherein the emitted optical output isintense enough to heat a magnetic recording medium sufficiently tofacilitate the recording of data.
 23. The apparatus of claim 1, whereinthe length of said aperture along an optical axis thereof isapproximately ¼-½ that of the average wavelength of the opticalradiation from said source.
 24. The apparatus of claim 1, wherein saidaperture has a spatial dimension that is less than ½ that of the averagewavelength of the optical radiation from said source.
 25. The apparatusof claim 1, wherein the optical radiation includes visible radiation.26. The apparatus of claim 1, wherein the optical radiation from saidsource has a fill width half maximum (FWHM) of less than about 0.1 timesthe average wavelength of the optical radiation.
 27. A method ofdirecting electromagnetic radiation onto a data recording medium,comprising: providing a metallic structure having an optical aperturetherein, one end of the aperture receiving optical radiation and anotherend of the aperture emanating optical output away from the structure,the structure having a transmission resonance corresponding to awaveguide mode of the aperture; directing optical radiation into theaperture at a frequency that matches the transmission resonance toenhance the optical output beyond what the optical output would be inthe absence of the transmission resonance; and directing the opticaloutput onto a data recording medium to facilitate the recording of data.28. The method of claim 27, wherein the data is readable by a processor.29. The method of claim 27, further comprising applying a magnetic fieldto the recording medium to write data into the recording medium.
 30. Themethod of claim 29, comprising heating the recording medium with theoptical output.
 31. The method of claim 30, wherein the dimensions ofthe aperture are chosen to enhance, at a predetermined frequency, theoptical output.
 32. The method of claim 30, wherein the recording mediumis granular and has a grain size on the order of between 10 and 250cubic nanometers.
 33. The method of claim 27, wherein the recordingmedium includes a medium selected from the group consisting ofmagneto-optic, phase-change, and chemical change media.
 34. The methodof claim 27, said directing optical output including positioning thedata recording medium and the metallic structure to within a wavelengthof each other, wherein the wavelength corresponds to the transmissionresonance.
 35. The method of claim 27, wherein the structure includes aprotrusion member that directs near-field optical output onto therecording medium.
 36. A method of directing electromagnetic radiationonto a recording medium, comprising: providing a metallic structurehaving an optical aperture therein, the structure having a transmissionresonance corresponding to a waveguide mode of the aperture; directingoptical radiation into the aperture at a frequency that matches thetransmission resonance to enhance optical output propagating out of theaperture and away from the structure; directing the optical output ontoa recording medium to heat the recording medium, thereby facilitatingthe recording of data; and reading back the data with a processor.
 37. Amethod of directing optical radiation onto a data recording medium,comprising: providing a metallic structure having an optical aperturetherein, the structure having dimensions selected to support opticalradiation propagating in a waveguide mode of the aperture; resonantlycoupling optical radiation into the metallic structure, the opticalradiation including a frequency that matches a transmission resonance ofthe waveguide mode; and directing optical output from the structure ontothe data recording medium.
 38. The method of claim 37, wherein themetallic structure adjoins at least one dielectric coating, wherein thethickness of said at least one dielectric coating is selected to enhancethe optical output from the aperture.
 39. The method of claim 37,wherein the optical radiation has a wavelength between 390 and 2000 nm.40. A laser, comprising: an optical gain medium through which opticalradiation is amplified; and a first reflector and a second reflectordisposed around said gain medium, wherein one of said reflectorsincludes: a metallic structure having an optical aperture therein, saidaperture having a first end and a second end, said first end receivingoptical radiation from said medium and said second end emitting opticaloutput, said structure having a transmission resonance corresponding toa waveguide mode of said aperture, wherein said transmission resonanceis at a frequency that matches a frequency of the optical radiation,thereby enhancing the optical output from said second end beyond whatthe optical output would be in the absence of said resonance.
 41. Thelaser of claim 45, further comprising a platform to which said laser issecured, wherein said platform is configured to be moved relative to adata recording medium while the separation between said structure and asurface of the data recording medium is kept to less than an averagewavelength of the optical output.
 42. The laser of claim 46, whereinsaid platform includes an air-bearing surface.
 43. The laser of claim45, further comprising at least one element secured to said laser, saidat least one element generating magnetic fields whose strength issufficient to write data in a data recording medium located within anear-field portion of the optical output.